As will be appreciated herein below, except as otherwise indicated, aluminium alloy designations and temper designations refer to the Aluminium Association designations in Aluminium Standards and Data and the Registration Records, as published by the Aluminium Association in 2013 and are well known to the person skilled in the art.
For any description of alloy compositions or preferred alloy compositions, all references to percentages are by weight percent unless otherwise indicated.
For this invention the term “sheet” or “sheet product” refers to a rolled product form up to 2.5 mm in thickness.
Generally, outer body panels of a vehicle require excellent physical properties in formability, dent-resistance, corrosion resistance and surface quality. However, the conventional AA5000-series alloy sheets have not been favoured because they have low mechanical strength even after press forming and may also exhibit poor surface quality. Therefore, 6000-series sheet alloys have been increasingly used. The 6000-series alloys provide excellent bake hardenability after painting and high mechanical strength as a result, thus making it possible to manufacture more thin-gauged and more light-weight sheets in combination with a class A surface finish.
U.S. Pat. No. 4,174,232 discloses a process for fabricating age-hardenable aluminium alloys of the Al—Mg—Si type using a specific annealing process. The disclosed aluminium is also embraced by the registered AA6016 alloy. The chemical composition of the registered AA6016 is, in wt. %:                Si 1.0 to 1.5        Mg 0.20 to 0.6        Fe up to 0.50        Cu up to 0.25        Mn up to 0.20        Cr up to 0.10        Zn up to 0.20        Ti up to 0.15,        
impurities each <0.05, total <0.15, balance aluminium.
The AA6016 rolled sheet products in the higher strength range when used for automotive parts are known to have limited formability and limited hemming performance.
There is a need for selection of aluminium alloy rolled sheet products and methods for producing vehicle parts or members providing good strength and levels of formability into vehicle parts.